Explain this Algebra problem.

[StaceyinLA]

5 - a = 1

 

Okay, so the answer is obvious, but, if you isolate the variable, and take the 5 from both sides, you get a -4. The question then is (from ds), how does 5 minus a -4 = 1. Clearly there is something we are missing with what happens to that minus sign - what is it??

[creekland]

5 - a = 1

 

subtract 5 from each side OR add a to each side

 

-a = 1 - 5 OR 5 = 1 + a (subtract 1 from each side if doing it this way)

 

-a = -4 (multiply by -1 if doing it this way) OR 5 - 1 = a

 

a = 4 or a = 4

[Dana]

5 - a = 1

 

Okay, so the answer is obvious, but, if you isolate the variable, and take the 5 from both sides, you get a -4. The question then is (from ds), how does 5 minus a -4 = 1. Clearly there is something we are missing with what happens to that minus sign - what is it??

 

That's why I recommend when learning this to show the steps on the same line rather than beneath - it's too easy to drop a sign.

 

So 5 - a = 1

Subtracting 5 from each side (and showing this!)

 

5 - a - 5 = 1 - 5

Now simplify:

- a = - 4

 

Note that the coefficient of a is -1, so we can multiply (or divide) by -1 on both sides, leaving a = 4.